Why is Ruby Slower on Mac? An Early Investigation

Sam Saffron has been investigating Discourse test run times on different platforms. While he laments spending so much extra time by running Windows, what strikes me most is the extra time on Mac — which many, many Rubyists use as their daily driver.So which bits are slow? This is just a preliminary investigation, and I’m sure I’ll do more looking into it. But at first blush, what seems slow?I’m curious for multiple reasons. One: is Mac is so slow, is it better to run under Docker, or with an external VM, rather than the Mac? Two: why is it slow? Can we characterize what is so slow and either do less of it or fix it?First, let’s look at some tools and what they can or can’t tell us.